The principal objective of the dam and reservoir is to protect downstream communities.  It is part of a network of five flood control dams in the Merrimack River Basin.  These dams work together to control flood waters during heavy rains and storms until rivers begin to drop and the stored water can be slowly and safely released.  Located approximately 8.6 miles above the confluence of the Blackwater and Contoocook Rivers. Blackwater Dam helps protect cities and towns from Concord, Manchester, and Nashua, New Hampshire to Lowell, Lawrence, and Haverhill, Massachusetts.

Responding to disaster, Congress authorized the US Army Corps of Engineers to build a system of flood control dams in the Merrimack and other New England river basins.  Blackwater Dam was completed in 1941 at a cost of $1.32 million and has already prevented $15.3 million in damages. The reservoir has a storage capacity of 15 billion gallons of water. To date, record high water occurred during the flood of April 1987.The reservoir was filled to 93% capacity with a water level of 564.1 mean sea level (msl). The normal level is 518 msl.

The Reservoir Regulation Team in Concord, Massachusetts is the nerve center for managing all the flood control dams in New England. Hydrologists and engineers use satellite communications and computer technology to constantly monitor river levels and weather conditions. They decide when and where to close the floodgates of the dams and store flood water in the reservoir valley.  The Blackwater Dam is a drybed Reservoir. The river flows through the dam unobstructed. Only when there is the threat of a flood do Corps personnel lower flood gates and begin to store water behind the dam.

For information on the current water levels please click the following link: Water Levels.